## Another curious Exocet (breaking all the rules ?)

Everything about Sudoku that doesn't fit in one of the other sections

### Another curious Exocet (breaking all the rules ?)

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`+-----------------------+------------------------+-----------------------+| 5      1389   9(134)  | 34679  -67(134)  4679  | 34678  2        13678 || 1489   6      9(1234) | 34579  -7(1234)  4579  | 34578  -5(134)  13578 || (124)  (123)  7       | 3456   8         2456  | 9      56(134)  1356  |+-----------------------+------------------------+-----------------------+| 1249   129    6       | 3479   5         479   | 37     8        137   || 48     7      5(4)    | 468-3  6(34)     1     | 2      56(3)    9     || 3      1589   59(1)   | 2      67        6789  | 567    56(1)    4     |+-----------------------+------------------------+-----------------------+| 69     359    59(3)   | 1      67(4)     45678 | 34568  569(34)  2     || 7      4      59(2)   | 568    6(2)      3     | 1      569      568   || 126    1235   8       | 456    9         2456  | 3456   7        356   |+-----------------------+------------------------+-----------------------+base: <1234>r3c12, targets: (r12c5 with a locked '1'), r2c8The bona fides:1r2c8 = (Skyscraper: (1)c38\r6)     - 1r3c12 : 2nd target false => base cells false2r2c5 = 2r8c5 - 2r8c3 = 2r2c3       - 2r3c12 : 1st target false => base cells false3r12c5,r2c8 = (FSF: (3)c358\r357b1) - 3r3c12 : both targets false => base cells false4r12c5,r2c8 = (FSF: (4)c358\r357b1) - 4r3c12 : both targets false => base cells falseFSF = Finned Swordfish (fins in b1)`

Adding "truth sets" for the base cells and the "locked 1", and "link sets" for the target cells, XSudo reports:

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`13 Truths = {1234C3 1234C5 134C8 3N12}17 Links = {1234r3 34r5 1r6 34r7 2r8 12n5 2n8 1234b1}5 Eliminations --> r12c5<>7, r1c5<>6, r2c8<>5, r5c4<>3`

Four of the eliminations are the usual target cell eliminations. The other one (r5c4 <> 3) can be explained using standard exocet properties and details about the strong links and weak links in the (3) swordfish.

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This was a "designed puzzle" -- designed to show some things that are possible, while avoiding distractions like secondary equivalences. It doesn't rate very high with SE (8.9), and the eliminations don't change the rating.

Broken rules (?):
1) r2c8 contains a '2', which is a base cell candidate -- not (currently) allowed for JExocet.
2) r12c5 contains a locked '1', which is also a base cell candidate -- same thing. (Allowed in Exocet definition(s) ?)

Neither of those things is a problem though, since the relevant digit is forced in to the "other target", if it's true in a base cell.
blue

Posts: 854
Joined: 11 March 2013

### Re: Another curious Exocet (breaking all the rules ?)

blue wrote:-

Broken rules (?):
1) r2c8 contains a '2', which is a base cell candidate -- not (currently) allowed for JExocet.
2) r12c5 contains a locked '1', which is also a base cell candidate -- same thing. (Allowed in Exocet definition(s) ?)

Neither of those things is a problem though, since the relevant digit is forced in to the "other target", if it's true in a base cell.

Nice findings

For me this is not an Exocet, it is another pattern to study.

One important point to classify it differently is that the "target " in column 5 can contain 2 digits of the base, to have it working as an exocet, you need more coming out of the other candidates for the digits of the base, what is shown for that puzzle in your xsudo diagram.

I have other ongoing tasks, but I keep that example in mind for later.
champagne
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Location: France Brittany

### Re: Another curious Exocet (breaking all the rules ?)

blue wrote:Four of the eliminations are the usual target cell eliminations. The other one (r5c4 <> 3) can be explained using standard exocet properties and details about the strong links and weak links in the (3) swordfish.

Swordfish ? If 3 is in the base, then in one of r5c58, if not, then in r5c5.
eleven

Posts: 2091
Joined: 10 February 2008

### Re: Another curious Exocet (breaking all the rules ?)

eleven wrote:
blue wrote:Four of the eliminations are the usual target cell eliminations. The other one (r5c4 <> 3) can be explained using standard exocet properties and details about the strong links and weak links in the (3) swordfish.

Swordfish ? If 3 is in the base, then in one of r5c58, if not, then in r5c5.

I just meant that you need most of the links in the swordfish, for the case where r3c2=3 and r2c8<>3 ... all but the 3c5 strong link, that you'ld use for the other cases.

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`3r3c2 - r12c3 = r7c3 - 3r7c8      \                  ||        -------------- 3r3c8                         ||                       3r2c8 (assumed false)                         ||                       3r5c8 - 3r5c4`

P.S. No, you're right. I never really appreciated the "true in the base -> true in (S-cells in) both S-cell rows" bit (until now, I guess).
P.P.S. It's a JExocet property, rather than an Exocet property, but it applies here, and it sure makes the argument easy.
blue

Posts: 854
Joined: 11 March 2013